Typically, with program controlled robot arms, a program of functions and coordinate data defining desired positions and orientations is defined and stored during a teaching or programming mode of operation. During the automatic mode of operation, the stored program is executed; and the robot arm moves to the programmed positions. The motion between the programmed positions may be point-to-point or along a controlled path. With point-to-point motion, the path between the programmed points is generally unknown and irregular. With controlled path motion, the path of the robot arm between the programmed points is along a known predictable path defined by the robot control, e.g. a straight line path. In either case, the locus of the programmed points represents the overall programmed path of the robot arm.
In both of the above cases, the actual path of the robot arm is limited to motion between the positions defined by the program. This is satisfactory in situations where the desired path of the robot arm is predictable and does not change from cycle to cycle. This is also satisfactory in applications where the exact path is not critical to the successful operation of the robot arm, e.g., spot welding, paint spraying, etc. However, there are situations where the exact path is critical but not constant. Using a traditional robot arm and control, to guarantee that the desired path exactly corresponds to the programmed path may require expensive and complex fixturing or manufacturing tolerances and handling procedures which are unacceptable in today's manufacturing environment.
Consequently, the need exists to provide a robot arm and control that functions in an environment in which the desired path is not predictable, nor repeatable from one cycle of operation to another. Such an application may be seam welding where two rough cut parts are manually tack welded together. In these situations, the seam will change from one pair of parts to another, and an exact path cannot be programmed in advance. In other situations, the robot arm may be required to remove the flashing from rough castings which will vary significantly from workpiece to workpiece.
Therefore, one object of the invention is to provide a robot arm and control which automatically responds to externally generated sets of input signals representing nonprogrammed points having a locus defining a desired, but unpredictable, nonprogrammed path.
Another object of this invention is to provide a robot arm and control having more flexibility in the automatic mode of operation by providing the capability of moving along a nonprogrammed path.
A further object of the invention is to provide a robot arm and control which dynamically responds to externally generated information for moving the robot arm to a series of nonprogrammed points having a locus defining a nonprogrammed path.
A further object of the invention is to provide a robot arm and control with the capability of responding to a programmed function code during the automatic mode of operation and accepting sets of input signals from an external path generator which define a number of nonprogrammed points.
A still further object of the invention is to provide a robot arm and control which in response to a programmed function code interrupts its automatic mode of operation, accepts nonprogrammed position and process function data from an external path generator, moves to the nonprogrammed points, executes the process function and resumes the automatic mode of operation.